A Short History of Hydrogen Sulfide

A Persistent False Trail

The great German biochemist Hoppe-Seyler became famous for his discovery of the abnormal form of hemoglobin known as methemoglobin, in which some or all of the heme irons have been oxidized to the ferric form. This reaction is readily mediated bothin vivo and in vitroby sodium nitrite. Methemoglobin cannot reversibly combine with oxygen, and the disruption of the oxygen-transport function of the blood can result in hypoxia and death.

In 1863, Hoppe-Seyler passed a stream of pure hydrogen sulfide through a sample of human blood and claimed to have observed a greenish pigment that was associated with shifts in the visible absorption spectrum of hemoglobin. Although he was aware that he had probably produced a mixture containing unstable and denatured products, which resulted in turbidity and precipitation and made the absorption spectra suspect, he still thought that the mixture contained a new form of hemoglobin. He called it sulfhemoglobin and thereby launched one of the most confused areas in hematology. It led to the hypothesis some still subscribe to—namely, that hydrogen sulfide is a blood poison like sodium nitrite and carbon monoxide. No matter that animal experiments clearly demonstrated that it was a respiratory toxin, or that no such pigment has ever been identified in the blood of animals or humans fatally poisoned with hydrogen sulfide. Sulfhemoglobin generated by hydrogen sulfide appears to be a strictly in vitrophenomenon, and it has yet to be prepared in pure form.